Electric heating element in knitted fabric

Abstract

An electric heating element is formed of a knit fabric and includes current supply wires and resistance wires which are incorporated in the heating element. The different types of wires extend mutually perpendicularly in the heating element. The conductive wires may be disposed in local or edge regions spaced apart with the knit fabric located therebetween. The knit fabric located between the conductive wires may be formed of non-conductive fibers or resistance wires.

What is claimed is: 
     
       1. An electric heating element comprising: a central mesh structure having a pair of edge portions;   a first and second conductive interlace mesh structure formed by knitting conductive, separated current supply wires, said first conductive interlace mesh structure being attached to one of said pair of edge portions of the central mesh structure and said second conductive interlace mesh structure being attached to the other of said pair of edge portions of the central mesh structure;   a plurality of electric resistance wires extending between and connected to the current supply wires forming the first and second conductive interlace mesh structures, such that the current supply wires supply current to the resistance wires, the resistance wires extending through and along the central mesh structure for supplying heat to the central mesh structure; wherein   each of the first and second conductive interlace mesh structures form a plurality of electrical connections with each of the resistance wires at each of the pair of edge portions of the central mesh structure such that the current supply to at least some of the resistance wires continues even upon at least one of breakage and inoperability of at least one of the conductive wires.   
     
     
       2. The electric heating element of claim 1, wherein the current supply wires are arranged generally to extend along the central mesh structure in one of the horizontal and vertical directions while the resistance wires are arranged to extend through the central mesh structure generally in the other of the horizontal and vertical directions. 
     
     
       3. The electric heating element of claim 1, wherein the electrically conductive wires are arranged spaced apart from each other on either side of the central mesh structure, the conductive wires forming each of the first and second conductive interlace mesh structures defining conductive regions extending generally perpendicular to a direction of extension of the resistance wires, the resistance wires extending through the first and second conductive interlace mesh structures. 
     
     
       4. The electric heating element of claim 3, wherein the central mesh structure located between the first and second conductive interlace mesh structures at least in part is comprised of a resistance wire and a knitted non-conductive fabric. 
     
     
       5. The electric heating element of claim 3, wherein the central mesh structure located between the first and second conductive interlace mesh structures is comprised of the plurality of resistance wires which are interconnected to form a resistive interlace mesh member which is located between the first and second conductive interlace members. 
     
     
       6. The electric heating element of claim 1, wherein the central mesh structure located between the first and second conductive interlace mesh structures at least in part is comprised of a resistance wire and a knitted non-conductive fabric. 
     
     
       7. The electric heating element of claim 3, wherein each of the first and second conductive interlace mesh structures has an edge region thereof connected to an adjacent edge portion of the central mesh structure. 
     
     
       8. The electric heating element of claim 7, wherein the connected edge regions of the first and second conductive interlace structures and the edge portions of the central mesh structure are partially knitted together. 
     
     
       9. The electric heating element of claim 3, wherein each of the first and second conductive interlace mesh structures is knitted onto the central mesh structure. 
     
     
       10. The electric heating element of claim 9, wherein the central mesh structure is comprised of the resistance wires, and the electrically conductive wires in the first and second conductive interlace mesh structures are knitted onto the resistance wires. 
     
     
       11. The heating element of claim 1, wherein at least one of the resistance wires and the current supply wires are provided with a corrosion and moisture resistant coating. 
     
     
       12. The heating element of claim 1, wherein the resistance wires are incorporated simultaneously as an addition to the central mesh structure. 
     
     
       13. The heating element of claim 12, wherein the resistance wire is twisted with the central mesh structure. 
     
     
       14. The heating element of claim 1, wherein the current supply wires are in the form of additionally knitted-in warp or weft yarns. 
     
     
       15. The heating element of claim 1, wherein the resistance wires are in the form of additionally knitted-in warp or weft yarns. 
     
     
       16. The heating element of claim 1, wherein the current supply wires and the resistance wires are incorporated in a three-dimensional weaving knit fabric. 
     
     
       17. A method of making an electric heating element, the method comprising the steps of: knitting a knitted mesh structure having first and second edge portions;   forming first and second conductive interlace mesh members from a plurality of electrically conductive, separated, current supply wires;   attaching the first conductive interlace mesh member to the first edge portion of the knitted mesh structure;   attaching the second conductive interlace mesh member to the second edge portion of the knitted mesh structure; and   attaching a plurality of resistance wires between the first and second conductive interlace mesh members so that the resistance wires extend from the first conductive interlace mesh member to the second interlace mesh member through the knitted mesh structure and so that each of the first and second conductive interlace mesh members form a plurality of electrical connections with each of the resistance wires so that current supply to at least some of the resistance wires continues even upon at least one of a breakage and inoperability of at least one of the conductive wires.   
     
     
       18. The method of claim 17, wherein at least said resistance wires are provided with a corrosion-resistant yet electrically conductive coating. 
     
     
       19. The method of claim 17, wherein the produced electric heating element is provided with a water-repellent, heat-resistant impregnation with one of a dispersion and a solution of one of a silicon resin and a fluorocarbon resin with subsequent drying. 
     
     
       20. The method of claim 19, wherein a cross-linkable silicon prepolymer is used and cross-linked one of during drying and after drying. 
     
     
       21. The method of claim 17, wherein the knitted mesh structure comprises the plurality of resistance wires which are interconnected to form a resistive interlace mesh member which is located between the first and second conductive interlace mesh members. 
     
     
       22. The method of claim 17, wherein the knitted mesh structure comprises a non-conductive textile fabric. 
     
     
       23. An electric heating element comprising: a central mesh structure having first and second edge portions and being formed of only a resistive interlace mesh structure consisting of a plurality of interconnected electrical resistance wires;   a first pair of conductive current feed wires attached to the first edge portion of the central mesh structure so as to be spaced from each other and to provide a plurality of electrical connections between each of the resistance wires and each of the first pair of conductive current feed wires; and   a second pair of conductive current feed wires attached to the second edge portion of central mesh structure so as to be spaced from each other and to provide a plurality of electrical connections between each of the resistance wires and each of the second pair of conductive current feed wires.   
     
     
       24. The electric heating element of claim 23, further comprising a first insulating thread superimposed on the resistance wires located at the first edge portion to mechanically support the first edge portion of the central mesh structure and a second insulating thread superimposed on the resistance wires located at the second edge portion to mechanically support the second edge portion of the central mesh structure. 
     
     
       25. The electric heating element of claim 23, wherein said central mesh structure extends in a substantially horizontal direction and said first and second pairs of conductive current feed wires extend in a direction substantially perpendicular to the substantially horizontal direction. 
     
     
       26. A method of making an electric heating element, the method comprising the steps of: forming a central mesh structure having first and second edge portions and being formed of only a resistive interlace mesh structure consisting of a plurality of interconnected electrical resistance wires;   attaching a first pair of conductive current feed wires to the first edge portion of the central mesh structure so that the first pair of conductive current feed wires are spaced from each other and form a plurality of electrical connections between each of the resistance wires and each of the first pair of conductive current feed wires; and   attaching a second pair of conductive current feed wires to the second edge portion of the central mesh structure so that the second pair of conductive current feed wires are spaced from each other and form a plurality of electrical connections between each of the resistance wires and each of the second pair of conductive current feed wires.   
     
     
       27. The method of claim 26, further comprising the steps of superimposing a first insulating thread on the resistance wires located at the first edge portion so that the first insulating thread supports the first edge portion of the central mesh member and superimposing a second insulating thread on the resistance wires located at the second edge portion so that second insulating thread supports the second edge portion of the central mesh member.